Earth's Hidden Groundwater Mapped for the First Time, Revealing the Water's Extent

Groundwater can be found throughout the globe, and is one of the most exploited resources on the planet. It ranges from months to millions of years old and now, researchers have mapped the extent of this precious resource.

With the growing global demand for water, it's important to understand how much water there is to use. This can allow for better use of water in the future, especially in the face of changing environmental conditions.

In this latest study, the researchers used multiple datasets, including data from close to a million watersheds, and more than 40,000 groundwater models to estimate a total volume of nearly 23 million cubic kilometers of total groundwater. Of this, about .35 million cubic kilometers is younger than 50 years old.

Why is it important to differentiate old groundwater from modern groundwater? Young and old groundwater are fundamentally different in how they interact with the rest of the water and climate cycles. Old groundwater is found deeper and is often used as a water resource for agriculture and industry. Sometimes it contains arsenic or uranium and can be more salty than ocean water.

So what did they find? The new map shows most modern groundwater in tropical and mountain regions. Some of the largest deposits are in the Amazon Basin, the Congo, Indonesia, and in North and Central America running along the Rockies and the western cordillera to the tip of South America.

"Intuitively, we expected drier areas to have less groundwater and more humid areas to have more, but before this study, all we had was intuition," said Kevin Befus, one of the researchers, in a news release. "Now we have a quantitative estimate that we compared to geochemical observations."